A scroll compressor has at least one of its wrap walls provided with an abradable coating to eliminate wrap leakage between opposed walls of the orbiting and non-orbiting scroll. The coating is only provided at radially inner locations, with radially outer locations being left to bear the load between the orbiting and non-orbiting scrolls.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, a pair of interfitting scroll members each have a base and a generally spiral wrap extending from its base. The wraps interfit to define compression chambers. One of the two scrolls is caused to orbit relative to the other. As the orbiting movement occurs, the wrap walls are brought into contact, and the wrap tips are brought into contact with the floor of the base of the opposed scroll. As the orbiting movement occurs, the compression chambers are reduced in volume, thus compressing the entrapped refrigerant.
A scroll compressor as known in the prior art is shown at 20 in FIG. 1. The orbiting scroll 22 is placed adjacent the non-orbiting scroll 24. The orbiting scroll 22 has a generally spiral wrap 26 extending from the floor 27 of its base. The non-orbiting scroll 24 has its own generally spiral wrap 28 extending from its base 29.
As shown in FIG. 2, this prior art compressor has contact between the flank walls of the scroll wraps 26 and 28 to define the compression chambers. As an example, one intended point of contact between the wraps 26 and 28 is shown at 30 and 32. These points of contact define compression chambers such as compression chambers 100 and 102. Other points of contact are shown at C. However, as shown in FIG. 3, there have sometimes been gaps such as gap 34 between the points 30 and 32. When this occurs, there is potential leakage between chambers 100 and 102 which will reduce the efficiency of the compression process. The gap 34 can be caused due to machining variations, thermal distortion, or other problems. Generally, such scroll compressors are “radially compliant,” allowing one of the wraps to move into abutting contact with the other at at least one point. However, as can be appreciated from FIG. 2, it would be desirable to have contact at several points C. It has been somewhat difficult due to the tolerance issues, etc. mentioned above, to ensure that each of the contact points will meet during operation. Again, this may result in a decrease in efficiency.
While coatings have been proposed for the wraps of scroll compressors, they have generally been along the entire length of the wrap. To have the coating along the entire length would have undesirable characteristics.